It is intended to stop patients suffering further attacks and developing heart failure, something existing treatments fail to do in many cases.

If the initial trials in London are successful, the treatment is likely to be extended to NHS hospitals across the country.

Researchers have called the project – the first of its kind in the world – “very exciting” and say it could have a significant impact on the annual toll of deaths from heart disease.

As well as saving lives, it would also reduce the £7billion-a-year burden of heart attacks on the economy through hospital admissions, drug prescriptions and lost working days.

Heart disease is the biggest killer in the UK. Every two minutes someone, somewhere, has a heart attack. When a patient reaches Accident and Emergency, they are currently given a treatment called angioplasty to re-open the blocked artery that triggered the problem.

This boosts survival rates and cuts repeated hospital admissions. But a significant proportion of patients will still be left with damage to their hearts.

Many people can end up with heart failure – in which the heart gradually loses its ability to pump blood and so leaves the person breathless and unable to move around.

Now two London NHS trusts – University College London Hospital and Barts and the London – plan to use stem cells to try to repair the damage immediately after a heart attack.

Stem cells are the basic building block cells that can grow and change into different types of tissue.

They have been shown to help people who already have heart disease by aiding the regrowth of damaged tissue.

The new trials, however, would be the first in the world to give patients the cells within hours of their heart attack in a bid to prevent any heart failure developing at all.

People who suffer a heart attack and are taken to the London Chest Hospital or London Heart Hospital for treatment will be asked for written consent to take part in the study.

After their angioplasty, those who agree will have stem cells removed from their hip using a needle under local anaesthetic.

The stem cells will then be placed in the same artery as the angioplasty – all within five hours of their original attack.

Doctors will then monitor the patients over the following months to establish how effective the stem cell treatment has been at preventing heart failure and repairing the damaged organ.

The research is being led by Professor John Martin, chair in cardiovascular sciences at the British Heart Foundation, and Dr Anthony Mathur of Barts and the London NHS trust.

Professor Martin said last night: “This is the first time in the world that stem cells have been used to stop the damage of acute heart attack.

“It is very exciting. We feel we can make a considerable reducstemtion in deaths and suffering from heart failure.”

The cost for each procedure has not yet been worked out. But Professor Martin said it would be very low as the cells come from the patients themselves, it does not prolong their hospital stay and the only expense is on needles and laboratory time separating out the muscle cells.

Dr Mathur said: “If we can demonstrate improvement in the quality of life of patients then this will be a significant step forward in the treatment of heart disease.

“Because the cells are taken from the patient themselves there are minimal ethical issues surrounding this procedure.

“There is also less likelihood of rejection complications.”

The research project, which is due to start after Christmas and will involve 100 patients, is being funded by the UK Stem Cell Foundation.

It is a randomised doubleblind controlled study which means half of the patients will be given stem cells and the rest just blood serum, to act as a comparison group.

Chief executive David Macauley said: “This is the first known project of its type in the UK to combine stem cell delivery to the heart with primary angioplasty – where the blocked arteries of heart attack patients are opened as quickly as possible.”

The doctors do not yet know whether the injected stem cells will turn into heart tissue and repair the damaged areas.

However, trials in other countries on heart patients – though not immediately after an attack – showed that their own stem cells successfully grew into heart tissue. Most medical research uses stem cells from human embryos because these are more adaptable and can grow into any type of bodily material.

A heart attack is caused by a blockage which prevents blood reaching the muscle and usually leads to a crushing pain in the chest, shortness of breath and dizziness.

Most people who suffer a heart attack remain conscious.

However many will go on to suffer a cardiac arrest, which is when the heart stops and the person loses consciousness and stops breathing.

Anyone who was unconscious at the hospital would not be able to take part in the trial as they could not give their consent.

Professor Peter Weissberg, medical director of the British Heart Foundation, said: ‘In the future, stem cells could herald a new frontier for heart patients.

“We welcome the research that helps us understand the potential role stem cells may yet play in treating heart disease.

“We hope that this study will compliment the BHF’s existing research in this area.”